Tutorial

If you honestly need pointers at the start of the game, you're not reading the in-game tutorial. That said, you're probably too A.D.D. to read a guide in regards to your problem, hence this is an exercise in futility to click on the tutorial section of a strategy guide. Makes you think, huh?

Killing Innocent Bystanders

You can speak to certain people while adventuring in the universe (not the Underverse) of Dick B. Riddick. If you do not need to kill certain NPCs, the game will not let you attack them. However, this NPC in the tutorial serves no purpose apart from being a dying target, so press your attack button and enjoy the bloodbath.

Notice that the forwards facing finisher is possible only against NPCs with low life (at 1 hit point). Enemies will have far more than 1 hit point, but if when you are fighting them and suddenly end the fight in a violent and abrupt manner, you will have defeated that enemy and you can move on to your next victim.

Ghost Drone Trio

The drone enemies in the Dark Athena chapter are primarily idiots ported from Thief: The Dark Project. Until they nudge Riddick in the dark or see him in plain daylight, they will patrol ceaselessly and without a care. The human mercs are often found more in aggressive mode (since they are tied to events) and are assigned to a specific task, or talking.

Drones are the only ones that can be in "low-alert" mode or "hi-alert" mode. If the lights on the drone are red, they are simply patrolling. If they are white, the drone uses the artificial human A.I. and are generally pursuing Riddick to murder his bald ass. White drones are far more dangerous than red ones (although red drones will also inspect disturbances in Riddick's imperfect stealth). However, all drones are as vulnerable to Riddick's backstab attack, as they were once human.

If you check out the Disney film The Black Hole, you will also find a plot where humans are made into machines.

Anyway, at the top of the ladder from where you killed the hapless Assassin's Creed reject, you can hide in the dark, stealth kill the drone (primary attack will neck snap, alternate attack will backstab and operate the gun instantly) then take the gun, fire it once, and draw out the other two losers. Note Riddick cannot move except backwards and he's more lit up than a gas-soaked anti-war effigy in the middle of the White House lawn. Hence take up a drone gun when you are in dire need of a weapon and are in a position to shoot enemies as they funnel through one path.

Human Mercs

The human mercenaries are as aggressive as the prison guards were in Butcher Bay, if not more annoying. However, there're no more lock-outs for guns, so almost any weapon Riddick comes across will be immediately usable (hence the large number of drones in some areas -- because you can't take a drone's gun).

Take out the mercenaries in the town square by using stealth fire. If Riddick is injured, flee to a dark space, crouch and regenerate the lost block. Sticking around to suck up gunfire is the fast way to die in Chronicles of Riddick. Riddick is never armored enough to suck up gunfire for more than 5 seconds before he dies.